Spectrophotometric determination of formaldehyde by using formaldehyde dehydrogenase

A new method for the determination of formaldehyde by using formaldehyde dehydrogenase is described. The method is based on the quantitative oxidation of formaldehyde with oxidized nicotinamide adenine dinucleotide (NAD⁺), in the presence of formaldehyde dehydrogenase, to form the reduced dinucleotide (NADH). This enzyme does not require glutathione as a co-factor and the NADH produced, which is directly proportional to the concentration of formaldehyde in the assay solution, is then measured spectrophotometrically at 340 nm. Formaldehyde can be determined in the range 0.3–8.0 μg ml^?1 (1.0×10^?5–2.7× 10^?4 M) with a sensitivity of 0.216 absorbance/ μg ml^?1 (0.0065 absorbance/μM). Optimal conditions and the selectivity of this enzyme toward formaldehyde are described.